1. Field of the Invention
The invention relates to apparatus for mounting an electric motor to permit the electric motor to be angularly displaced about a composite center of gravity of the electric motor and mounting apparatus, and more particularly, to apparatus for mounting a capstan drive motor to permit angular displacement with only a single degree of freedom about the composite center of gravity.
2. Description of the Prior Art
Magnetic tape cartridges are commonly used by data storage in digital computer processing equipment. Magnetic tape cartridges of the type used in digital data applications include a tape capstan which is frictionally engaged with a motor capstan driven by an electric motor when the tape cartridge is inserted into a tape transport to impart motion to the magnetic tape within the cartridge. The electric motor is ordinarily mounted so that it pivots slightly when the motor capstan frictionally engages the tape capstan when a tape cartridge is inserted into the tape transport. The motor mounting system provides counterforce which maintains a predetermined pressure between the motor capstan and the tape capstan so that magnetic tape is drawn past recording heads or playback heads at a constant rate to ensure accurate data recording or playback. It is highly desirable that the above mentioned pivoting occurs about the composite center of gravity of the electric motor capstan, and motor mounting system so that constant capstan pressure is maintained regardless or orientation (i.e. vertical, horizontal, etc.) of the transport. It is also important that the above described pivoting occur about the composite center of gravity so that the capstan pressure will be uniform if the tape transport is subjected to acceleration, shock or vibration. These factors are especially important if the tape transport is utilized in equipment which is normally subjected to acceleration, vibration, shock, etc. It is noteworthy that tape transports are commonly used in portable electronic equipment which is subjected to such conditions.
It is therefore an object of the present invention to provide a capstan motor mounting system which provides more accurate and uniform motor capstan pressure and more constant tape capstan speed than capstan motor mounting systems of the prior art.
It is highly desirable that capstan motor mounting systems have the lowest possible mass so that the amount of mass to be pivoted about the composite center of gravity when magnetic tape cartridges are inserted into the tape transport is minimized. Prior tape transport systems cause some difficulty in inserting magnetic tape cartridges because of the high mass associated with the capstan motor mounting system; such mass, along with the mass of the capstan motor, must be suddenly displaced by the pressure of the tape capstan against the motor capstan. This causes difficulty in cartridge insertion, and increases stresses on the motor mounting parts, thereby decreasing system reliability. Further, high mass capstan motor mounting systems are much more likely to be seriously damaged if the unit is dropped or subjected to other types of shock.
It is therefore an object of the invention to provide a capstan motor mounting system which has substantially less mass than prior art capstan motor mounting systems.
The closest known prior art capstan motor mounting system is described in U.S. Pat. No. 4,085,906, issued Apr. 25, 1978 to Dahl et al. That capstan motor mounting system includes a mounting plate having a cylindrical aperture therein and means for attaching the mounting plate to the capstan motor. The plane of the mounting plate passes directly through the center of gravity to the capstan motor. The mounting plate includes three apertures located at three apexes of an imaginary triangle symmetrically positioned about the cylindrical opening in which the capstan motor is supported. Three shoulder bolts extend through the three apertures and are firmly affixed to a rigid support. Three bias springs disposed about the three shoulder bolts support the mounting plate, so that it can be tilted in one plane by pressure on the motor capstan, causing displacement of the capstan motor and mounting system about the center of gravity of the capstan motor. This system has a number of moving parts, and is subject to the difficulty that the shafts of the shoulder bolts may frictionally engage the interiors of the triangularly located apertures causing variations in motor capstan pressure and tending to cause angular displacement of the capstan motor about a point other than the composite center of gravity. This can cause inaccuracies in recording or play back.
It is therefore an object of the ivnention to provide a mounting system for a capstan driving motor, which mounting system produces a constant driven capstan speed regardless of the direction of acceleration or shock applied to a tape transport in which the motor and mounting system is installed.
It is another object of the invention to provide a motor capstan mounting system having less mass than those of the prior art.
Other patents, deemed less relevant than the above patent, uncovered in a novelty search directed to the present invention, include U.S. Pat. Nos. 1,679,990, 2,558,541, 2,565,733, 2,690,891, 3,432,082, 3,625,466, 3,836,100 and 4,008,841.